A dispersion of polytetrafluoroethylene is industrially produced by the polymerization of tetrafluoroethylene monomer dispersed in an aqueous phase either in the form of emulsion or suspension in the presence of an emulsifying or a dispersing agent, using free radical-generators as catalysts. It is also known that said process can be carried out by initiating the polymerization with ionizing radiation instead of using free radical-generators in the presence of either emulsifying or dispersing agent. Radiation-initiated polymerization is convenient, because it is easier to control the reaction. However, according to the present inventors' detailed studies, the molecular weights of the polymers obtained by said radiation-initiated polymerizations were at most 1,000,000 or so, and this is remarkably low compared with those of the polymers obtained by the free radical polymerizations. Accordingly, the molded articles obtained from the polymers obtained by radiation-initiated polymerization have defects in that their mechanical strength is low, which is very disadvantageous from a practical viewpoint. Experiments to increase the molecular weights of such polymers by applying the "post-irradiation polymerization method" thereto have been made, but, without success.